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This design is (we feel) fairly learnable at the cost of efficiency. It uses prompts to help the user navigate the site and find the tutorial they need, reducing the task of finding out how the website works to simple point and click operations. As a result, however, it is more difficult to speed to a specific tutorial and requires a lot of user interaction. User interaction is almost always a cause of slowdown and there are lots of tasks here. It should be offset by the fact that the target audience may not be able to accomplish their task with a more efficient interface. We imagine that the UI would have navigation elements to make it easy to backtrack in the event that the user clicks the wrong button. It is also fairly safe to use because there aren't many elements which, if the user performed the wrong action with, would put them in an irrecoverable state or make some change that they couldn't undo.
S&D 2
This design's homepage is centered around a large searchbar which suggests tutorials as key words are typed in, making it extremely efficient. A selection of commonly viewed tutorials is also available below the search bar for even quicker access. The tutorial view itself is structured so you can see at a glance how much more there is to the tutorial and skip around very easily. While a moderately skilled user could learn this interface easily, it probably suffers from usability issues with the unskilled user class because of the computer-intuition required. Anyone who can use a search bar will have an easy time using the home page, at least, but the slide interface of the tutorials, while easy to use, might be offputting to some. The slide model has the property that despite looking daunting at first, it is actually fairly easy to go forwards and backwards. As a result, any misplaced clicks or confused actions are safe and easily recovered from.